1. Field of the Invention
The present invention relates to a Power Headroom Report (PHR) method and apparatus of a User Equipment (UE). More particularly, the present invention relates to a method and apparatus for reporting Power Headroom (PH) of a UE efficiently.
2. Description of the Related Art
Mobile communication systems are developed to provide subscribers with voice communication services on the move. With the advance of technologies, the mobile communications have evolved so as to support high speed data communication services as well as the standard voice communication services.
Recently, as one of the next generation mobile communication systems, Long Term Evolution (LTE) is on the standardization by the 3rd Generation Partnership Project (3GPP). LTE is designed to provide for a downlink speed of up to 100 Mbps. In order to fulfill the requirements of the LTE systems, studies have been done in various aspects, including minimization of the number of involved nodes in the connections, and placing the radio protocol as close as possible to the radio channels.
In the meantime, unlike the standard voice service, most data services are allocated resources according to the amount of data to be transmitted and to the channel condition. Accordingly, in the wireless communication system such as cellular communication system, it is important to manage resource allocation based on the resource scheduled for data transmission, the channel condition, and the amount of data to be transmitted. This is the fact even in the LTE system, and even if the base station scheduler manages and assigns radio resources.
More recent studies are focused on the LTE-Advanced (LTE-A) for improving data rate with the adaptation of several new techniques. Carrier Aggregation (CA) is one of the most distinct features of LTE-A. Unlike communication systems according to related art that use single uplink and single downlink carriers per a User Equipment (UE), the Carrier Aggregation enables a UE to be scheduled on multiple carriers in both uplink and downlink. Accordingly, it is required for the eNB to configure the UE transmit power per uplink carrier efficiently and, as a consequence, it becomes more important for the UE to report maximum UE transmit power and Power Headroom (PH).
Meanwhile, LTE UEs are generally configured to be equipped with multiple system modems enabling operation in dual mode. This configuration allows the UE to simultaneously receive multiple services through two different systems. In such a situation, the UE is required to report the maximum transmit power and Power Headroom (PH) per system in order to improve scheduling reliability.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.